Flow Graph Analyzer is delivered with the Intel® Advisor. You can find out more information about Intel® Advisor and instructions on how to obtain it and its components at https://www.intel.com/content/www/us/en/developer/tools/oneapi/advisor.html.
You can download or find out more about the Intel® oneAPI Threading Building Blocks library at https://www.intel.com/content/www/us/en/developer/tools/oneapi/onetbb.html or https://github.com/oneapi-src/oneTBB.